San Francisco 49ers

49ers to be without Foster, Tartt against Raiders; Beathard, Sherman and Breida listed as questionable

The 49ers will be missing a pair of key players in the middle of their defense during Thursday night’s game against the Oakland Raiders — and other starters will be game-time decisions.

The team announced Wednesday linebacker Reuben Foster (hamstring) and strong safety Jaquiski Tartt (shoulder) will not play. Additionally, quarterback C.J. Beathard (right wrist), cornerback Richard Sherman (calf, heel), running backs Matt Breida (ankle) and Raheem Mostert (ankle), receiver Pierre Garçon and center Weston Richburg (knee) are listed as questionable.

Foster’s injury makes it likely Malcolm Smith returns to play in Foster’s “Will” linebacker spot after spending the bulk of the season working as the “Sam” on the strong side of formations. But the strong safety position is far less certain.

Tartt’s backup, Antone Exum Jr., was also ruled out Wednesday after suffering a concussion during the loss Sunday to the Arizona Cardinals. That means either third-stringer Tyvis Powell — who was moved from cornerback in August — or rookie sixth-round draft pick Marcell Harris would start in Tartt’s place.

The 49ers have until 1 p.m. Thursday to add Harris to the active roster, off injured reserve following a preseason hamstring injury. The Florida alum missed all over 2017 after suffering an Achilles tear the previous summer. San Francisco liked his physicality with the Gators and potential on special teams.

Beathard accidentally banged his throwing hand against a helmet during the first half of Sunday’s defeat and had his wrist and thumb heavily wrapped while speaking to reporters Tuesday. Coach Kyle Shanahan withheld Beathard from the afternoon walkthrough because he was struggling to grip a football. But since he was ruled as “questionable,” he might have made progress during Wednesday’s session.

The 49ers would call on second-year pro Nick Mullens if Beathard can’t play. Mullens began the year on the practice squad, which is where he spent all of 2017 after going undrafted out of Southern Mississippi. He was elevated to the active roster after Jimmy Garoppolo went down with a season-ending left knee injury in September. Mullens has never taken a regular season snap.

Sherman’s calf has been bothering him periodically throughout the season after he spent the spring rehabbing an Achilles tear. He missed the loss Week 4 to the Chargers after tweaking it in the first half the previous week against the Chiefs, but then returned earlier than expected the following week for a home game against the Cardinals.

The 49ers this week released cornerback Greg Mabin, presumably to clear a roster spot for Harris and linebacker Dekoda Watson as they return from injured reserve. It’s unlikely the team would have let Mabin go if it believed Sherman wasn’t going to play.

Breida has been dealing with ankle, knee and shoulder injuries throughout the season and has been listed as questionable in five of the last six weeks, but hasn’t missed a game. Mostert tweaked his ankle in Arizona.